ESCA studies of the coordination state of aluminium in oxide environments

X-Ray photoelectron spectroscopy (known as XPS or ESCA) can differentiate between tetrahedral and octahedral Al atoms in inorganic solids. Although primarily used for the study of aluminosilicates, this semi-quantitative technique is applicable to other materials, irrespective of whether they contain aluminium in one or more coordinations with respect to oxygen. If less sensitive to the coordination of Al, the range of ESCA, a surface-oriented technique, is thus not very different from that of the bulk-oriented solid-state NMR. The procedures described here are successful with any high-resolution ESCA system, but are greatly facilitated by hood gun technology which removes insulator-induced charging shifts. Areas of potential difficulty are also discussed.